4-6 times each yr the car bucks violently when placed into reverse, 1-4 hours after last use, never when cold or hot. Placing it back into Park or Neutral cancels the bucking and it can be placed into reverse as though nothing had ever happened. It will continue to buck for at least as long as 10 seconds with no change until I get scared and shift into P or N. Thanks.

I have the same issue with my 2003 a4. I just got in dec. and it started happening in March/April. Has happened 5 times total including today. I am too nervous to bring it in and find out it will require a new transmission. Did you figure out the issue?

While I empathize with your dilemma, I have to point out two unfortunate truths:

The OP, perry cohn, is most likely not still lurking on this site after posting his problem almost 4 years ago. Nobody had a suggestion for him in July, 2007, and I sincerely doubt that he is still awaiting a response in June, 2011.

The problem with your car will not fix itself. By delaying diagnosis and repair, you are almost definitely ensuring that the inevitable repair bill will be higher. Deferred repairs are never cheaper, and are almost always more expensive.

All of that being said, I strongly suggest that you take the car to an independent VW/Audi specialist. Many areas have these indy shops because of the very high fees charged by VW and Audi dealers, and because of the very high breakdown rate of these cars as they age. Even if this specialist gives you bad news, the cost of fixing the problem will likely be FAR cheaper than if you went to an Audi dealer.